Perfect for adult coloring. They do not pierce behind the sheet (to water and not to the alcohol). I will not for a long time so no idea about using their lifespan. They are a bit expensive but the storage box is very convenient; it unfolds for a presentation of the colors straight. Thereafter I will redeem worn felts unit. The colors are well pigmented, I associated this format 68 (points "thick") to the same product but 88 advanced (small point - 0.4 mm), This allows me to keep the same colors, as well as details of the drawing I uses one or the other point on the same coloring. I recommend